1. Field of the Invention
This invention relates to an apparatus capable of engaging and retaining bowed substrates thereto. More particularly, this invention relates to an improved apparatus, comprising a flexible vacuum seal pad structure capable of enhanced retention of non-planar substrates thereto.
2. Description of the Related Art
Movement of substrates such as silicon semiconductor wafers from one process chamber to another chamber is commonly done with remote equipment such as, for example, robotic apparatus with minimal manual handling of the substrate. This requires secure retention of the substrate (usually the backside of the substrate) to the apparatus carrying out the movement of the substrate. Referring to prior art FIGS. 1–6, FIG. 1 shows a portion of a typical prior art robotic apparatus generally indicated by arrow at 2 and having a robotic arm, generally indicated at arrow 4, attached thereto. A flat finger apparatus or endeffector, generally indicated in the prior art embodiment of FIGS. 1–3 at arrow 10, is generally U-shaped, with a short stub arm 12, at the bottom of the U, which is attached to robotic arm 4 at 14, as seen in prior art FIG. 1.
The prior art generally U-shaped finger apparatus 10 shown in FIGS. 1–3 is typically provided with two flat fingers 16 and 18, which comprise the side portions of the U-shape of finger apparatus 10. Fingers 16 and 18 contact the underside of the substrate being transported (in the prior art apparatus of FIGS. 1–3) through three identical vacuum pad mechanisms mounted thereon, as generally indicated by arrows 30, 32, and 34 in FIGS. 1–3.
FIG. 4 shows a variation of the prior art wherein a single finger apparatus 10′ is shown which is capable of being attached to an arm of a robotic apparatus (not shown). Since only a single finger apparatus is used in this prior art embodiment, only two vacuum pad mechanisms 32 and 34 are shown,
FIG. 5 shows, in more detail, one version of a typical prior art vacuum pad mechanism 34, representative of the construction of identical vacuum pad mechanisms 30 and 32 as well. A large bore 40 is shown formed partially through finger 18 of finger apparatus 10 perpendicular to the surface of finger 18. A smaller bore 44 is then formed completely through the remainder of finger 18 to intersect a covered groove 46 formed in the opposite surface of finger 18, to provide communication between vacuum pad mechanism 34 and an external vacuum pump (not shown) which forms no part of this invention. Received in large bore 40 is a circular seal 50 having an OD slightly larger than the diameter of large bore 40 to thereby form a seal between seal 50 and the sidewall of large bore 40. All of the bottom surface of seal 50 is conventionally secured to the bottom wall of large bore 40 by an adhesive.
Seal 50 is provided with a central bore 54 concentric with small bore 44 in finger 18 of finger apparatus 10, and having the same diameter as central bore 44 as well. Seal 50 is further provided with an upstanding peripheral lip 56 on its upper surface 52, thereby defining a vacuum plenum 58 between lip 56 and upper surface 52 of seal 50 and the undersurface of a substrate as shown in FIG. 5. When a flat substrate 60 is engaged by vacuum pad mechanisms 30, 32, and 34, the vacuum plenum formed by seal 50 of each vacuum pad structure 30, 32, and 34 draws substrate 60 snugly against vacuum pad structures 30–34 while robot arm 4 and finger apparatus endeffector 10 thereon move substrate 60 to its desired destination.
In a perfect world where substrate 60 would always be perfectly flat before, during, and after processing, the problem which this invention seeks to solve would not exist, at least not to the extent of the problem described above. However, as shown in exaggerated form in prior art FIG. 6, warped or bowed substrate 60′, cannot enter into the previously described sealing relationship with vacuum pad mechanism 30, 32, and 34, since the rigid prior art structure has little if any flexibility to permit the vacuum pad mechanism 30, 32, and 34 to compensate for the bowed condition of substrate 60′. Since a vacuum seal is not established between vacuum pad mechanisms 30, 32, and 34 and warped or bowed substrate 60′, substrate 60′ is not secured to finger apparatus 10. This, in turn, means that substrate 60′ is free to slide on the upper portions of fingers 16 and 18 of finger apparatus 10, which is an unacceptable condition.
FIG. 7 shows a prior art modification of the above described vacuum pad mechanisms 30, 32, and 34 wherein a barrel-shaped opening 20 is formed in a base member or finger 19. A seal structure 22 comprising a flexible material having barrel-shaped sidewalls thereon slightly larger than the barrel-shaped openings 20 in finger 19. Seal structure 22 is inserted into barrel-shaped opening 20 to provide a fit tight enough to be gas-tight, yet not so tight as to prevent or inhibit seal structure 22 from tilting in its respective barrel shaped opening formed in finger 19 to thereby provide some degree of adjustment for non-planar wafers.
While the foregoing may constitute an improvement over the earlier described prior art structures and practice previously described, it still would be desirable to provide an apparatus comprising one or more flexible vacuum seal pad structures capable of sealingly engaging even a bowed substrate to permit movement of the substrate from, for example, one processing station to another while maintaining securement of the bowed substrate to the finger apparatus.